This invention relates generally to catheters adapted to be inserted into the cardiovascular system of a living body and, more particularly, to a preshaped catheter having an improved distal end portion for providing more precise access to the right main coronary artery of the cardiovascular system.
Catheters are often used in the performance of medical procedures such as coronary angiography for injecting dye, or the like, into the cardiovascular system for diagnosis; and angioplasty to widen the lumen of a coronary artery which has become at least partially blocked by a stenotic lesion causing an abnormal narrowing of the artery due to injury or disease. In these techniques the distal end of a therapeutic catheter is introduced into the aorta by way of the femoral artery. The proximal end of the catheter is then manipulated so its distal end is inserted into the lumen of a selected coronary artery branching off from the aorta. A typical treatment procedure would involve initially inserting a guiding catheter into the cardiovascular system in the above manner, followed by the introduction of a suitable therapeutic device, such as a dilating catheter, a laser catheter, an atherectomy catheter, or the like. The therapeutic catheter is guided through the guiding catheter until its distal end portion is positioned adjacent the stenotic lesion in the coronary artery for use in reducing the blockage in the artery. In all such medical procedures, it is absolutely essential that the guiding catheter has the appropriate shape for proper alignment of its distal end relative to the coronary artery.
The most common catheter used in treatment of the right main coronary artery is what is often referred to as a "Judkins" catheter, which has a specially shaped distal end portion for facilitating insertion and engagement into the right coronary artery. However, there are some significant disadvantages to the "Judkins" catheter, such as its frequent inability to align perfectly coaxially with the selected artery and thus permit optimal treatment, and its inability to adequately support other therapeutic devices such as balloon catheters. Also, the Judkins catheter requires a 180 degree rotation and adroit manipulation to selectively engage its distal end in the right main coronary artery, which makes it more difficult to use effectively and efficiently.
In FIGS. 1A and 1B of the drawings, the reference numerical 10 refers, in general, to a well known prior art catheter, commonly referred to as a "Judkins" catheter. The catheter 10 is in the form of an elongated tubular member having a straight portion 12 (shown partially in FIGS. 1A and 1B) and a distal end portion. The distal end portion consists of a tertiary curved portion 14, a secondary curved portion 16, a primary curved portion 18, and a tip portion 20. The tertiary curved portion 14 extends from the straight portion 12 and is bent to form a curve of approximately 30.degree.. The secondary curved portion 16 extends from the tertiary curved portion 14 and is bent in the opposite direction to the tertiary curved portion 14 to form a curve of approximately 30.degree.. The primary curved portion 18 extends from the curved portion 16 and is bent to form a curve of approximately 90.degree. and the tip portion 20 extends from the curved portion 18. According to a typical Judkins catheter the curved portions 14 and 16 would have a radius of curvature of 10 and 5 centimeters ("cm."), respectively, and the tip portion 20 would have a length of 1 cm. The catheter 10 is usually fabricated of a plastic material selected to exhibit flexibility and softness yet permit adequate "torque control" (i.e., the ability to transmit twisting forces along its length) so that it can be located and maneuvered precisely within a cardiovascular system by skilled manipulation of its proximal end, as will be described.
A typical cardiovascular system is shown in FIGS. 1C and 1D and is referred to, in general, by the reference numeral 22. The system 22 includes an aorta 24 comprised of a descending aorta 24a, an ascending aorta 24b, and an aortic arch 24c which extends from the descending aorta 24a to the ascending aorta 24b over a curve of approximately 180.degree.. The ascending aorta 24b then branches through a right ostium 26 and a left ostium 27 into a right coronary artery 28 and a left coronary artery 30, respectively. An aortic valve 32 extends between the right coronary artery 28 and the left coronary artery 30 and is connected to the heart (not shown). As better shown in FIG. 1D, the right coronary artery 28 and the left coronary artery 30 are normally angularly spaced approximately 120.degree..
The prior art Judkins catheter 10 of FIGS. 1A and 1B is designed for use as a diagnostic catheter in the right coronary artery 28 but is also used as a guiding catheter for treatment of stenotic lesions, or the like. To this end, the catheter 10 is inserted into the system 22 and is manipulated so that, ideally, the tip portion 20 of the catheter 10 is positioned through the ostium 26 and into the lumen of the right coronary artery 28 and used to guide other therapeutic devices such as balloon, laser or atherectomy catheters, or the like (not shown) into the right coronary artery 28.
To assist in advancing the catheter 10 through the system 22, a relatively stiff wire is initially inserted into the catheter 10 to straighten it. After the catheter is inserted into the ascending aorta 24b, the wire is withdrawn, causing the catheter to position itself along the wall of the ascending aorta 24b, 1 to 2 cm. above the ostium 27 of the left coronary artery 30. As a result, the tip portion 20 of the Judkins catheter 10 points away from the ostium 26 of the right coronary artery 28 and must be rotated 180.degree.. During this rotation, the catheter 10 will suddenly descend about 3 cm. until the tip portion 20 hopefully aligns with the ostium 26 of the right coronary artery 28 in a coaxial relationship as shown in FIG. 1C.
However, due to the particular configuration of the Judkins catheter 10, the tip portion 20 is often misaligned with the ostium 26 of the right coronary artery 28 and is not located coaxially with the latter artery. Thus, when an inner catheter or therapeutic device such as a balloon catheter (not shown) is passed through the catheter 10, the former often strikes the wall of the ascending aorta 24b or the right coronary artery 28 increasing the risk of damage. Also, due to the fact that the curved portion 18 is positioned adjacent to the wall of the ascending aorta 24b which contains the ostium 26 of the right coronary artery 28 and is a considerable distance from the wall of the ascending aorta 24b opposite the ostium 26, the catheter 10 does not provide support for other catheters or devices that are passed through the catheter 10. This problem is described in depth in Danforth U.S. Pat. No. 4,909,787. Due to the lack of support, when axial forces are exerted on the tip portion 20, such as when a dilation balloon is advanced, the tip portion 20 has a tendency to push back from the ostium 26 causing the tip portion 20 to dislodge from the lumen of the right coronary artery 28 and the therapeutic device to prolapse in the ascending aorta 24b. Thus, the therapeutic device loses its preferred orientation within the ascending aorta and right coronary artery. After this occurs, further advancement of the therapeutic device becomes nearly impossible because the Judkins catheter no long provides adequate support to the highly flexible shaft of the therapeutic device as one attempts to push the therapeutic device across the tight stenosis.
The lack of "backup" support happens because the Judkins catheter was not originally intended to serve as a conduit for other therapeutic devices into a patient's arterial system. Rather, the Judkins catheter was designed and configured merely to provide a means for introducing contrast fluid into the aortic root and main coronary artery region.
Various attempts to address these problems are described in the prior art. One of these attempted solutions is the Arani Double Loop guiding catheter. This catheter is illustrated and described in Arani, A New Catheter For Angioplasty of the Right Coronary Artery and Aorto-Coronary Bypass Grafts, Catheterization and Cardiovascular Diagnosis 11:647-653 (1985) and in a videotape publication, Select Curve Guiding Catheters: Cannulating the Right Coronary Artery, USCI/C.R. BARD (1988).
In FIGS. 2A, 2B and 2C, the Arani-type Double Loop guide catheter for the right coronary artery is presented to illustrate its use and the attendant difficulties and deficiencies of the Arani-type catheters for catheterization of the right coronary artery when used for angioplasty.
The Arani catheter is shown in FIG. 2A in a relaxed or "equilibrium" state prior to insertion into the cardiovascular system. The Arani-type Double Loop guide catheter includes a first straight proximal portion 402, a secondary curve portion 404, a second straight distal portion 406, a primary curve portion 408, and a distal tip straight portion 410 having a tip 412.
The Arani-type Double Loop catheter 400 is shown disposed in a cardiovascular system 500 from a left anterior oblique (LAO) view as seen under fluoroscopy by the physician as shown in FIGS. 2B and 2C. The cardiovascular system includes a descending aorta 502, an aortic arch 504, and head and neck vessels 506 extending from a roof 508 of the aortic arch 504. The aortic arch also has a floor 510. The cardiovascular system 500 further includes an ascending aorta 512 having an antero-lateral wall 514 and a postero-medial wall 516. A right main coronary artery 518 extends from the antero-lateral wall 514 of the ascending aorta and has an ostium 520 defining the interface between the ascending aorta 512 and the right coronary artery 518. A left main coronary artery 522 extends from the opposite wall of the ascending aorta 512 and has an ostium 524. A Sinus of Valsalva 526 extends below both the ostia of the left and right coronary arteries. The Sinus of Valsalva defines an area behind each cusp of the aortic valves where the aortic vessel wall bulges outward, forming a pouch-like dilatation. The Sinus of Valsalva 526 has a diameter wider than the diameter of the ascending aorta and have a wall having a curvature greater than that of the ascending aorta.
For use, the Arani catheter 400 must be first be maneuvered into the aortic complex. This is accomplished by advancing the catheter 400 over a stiff guide wire into the ascending aorta 412 to prevent the tip 412 from entering the great neck arteries. After removing the guide wire, the tip 412 typically is positioned against the antero-lateral wall 514 of the ascending aorta 512. With some downward or upward movement, the tip 412 will usually enter the ostium 520 of the right main coronary artery 518. As seen in FIG. 2B, the tip 412 of the Arani catheter 400 is marginally intubated into the ostium 520 of the right coronary artery 518.
The Arani catheter offers two ways to use the catheter to get backup support. The first way is the "fulcrum position" (FIG. 2B) where the tip of the Arani catheter is intubated into the ostium of the right coronary artery and a portion of the straight arm of the catheter is anchored against the opposite ascending aortic wall. The second way is the "buttressed position" (FIG. 2C) where the tip of the Arani catheter is positioned in the ostium of the right coronary artery, and then the catheter is advanced distally so that the secondary curve of the catheter contacts the antero-lateral wall of the aorta. As seen in FIG. 2B, the fulcrum position is achieved by pulling the catheter 400 proximally backward, with the tip 412 engaged in the ostium 520, so that the straight portion 406 of the catheter 400 contacts the postero-medial wall 516 of the ascending aorta 512. In addition, a more proximal portion of the catheter (the first straight proximal portion 402) contacts some portion of the wall (floor) of the proximal portion of the aortic arch 510. In this fulcrum position, the Arani catheter 400 attempts to provide backup support by gaining leverage off the postero-medial wall 516 of the ascending aorta. This leverage is created by pulling proximally backward on the catheter 400 which causes the tip 412 of the catheter 400 to tend to further seek the ostium 520. This leveraging is intended to counter stenotic pushback forces acting to push the tip 412 out of engagement with the ostium 520 of the right coronary artery 518.
However, the Arani catheter 400 when used in the fulcrum position has several major disadvantages. First, the Arani catheter 400 as used in the fulcrum position lacks stability. The catheter is limited from making substantially contiguous contact with the postero-medial wall 516 of the ascending aorta 512 and the inner wall (floor 510) of the aortic arch 504 throughout its length because the 90.degree. secondary curve portion 404 forms such a relatively sharp bend in the catheter. This lack of contact created by the sharp bend provides less frictional engagement for the catheter to resist slippage when countering stenotic pushback forces. Second, this relatively sharp secondary curve of the catheter 400 in use inhibits achieving a direct and positive correspondence between advancement of the proximal end of the catheter and advancement of the tip 412 of the catheter into the ostium. This relatively severe bend retained in the catheter 400 in use distorts the 1:1 tip response that might otherwise occur in a catheter with relatively smooth curves along its entire length, from the proximal end to the distal end.
A third major disadvantage of using the Arani catheter in the fulcrum position is a lack of direct superior backup support which is created by negative correspondence between advancement of the proximal end of catheter and advancement of tip of catheter. As the Arani catheter 400 is moved into the fulcrum position, the tip moves distally forward but the heel (the proximal end of the primary curve of the catheter) moves away from a distal portion 517 of the postero-medial wall 516 of the ascending aorta to hang suspended in the ascending aorta adjacent the ostium 524 of the left coronary artery 522. This negative correspondence between advancement of the catheter's proximal end and the catheter's tip is a result of the fulcrum effect created by the balancing of the straight segment on the postero-medial wall 516. Moreover, in this fulcrum position the tip 412 can prolapse, i.e., become disengaged from the ostium 520, because there is no direct support because of the lack of contact between the heel of the catheter 400 and the distal portion 517 of the postero-medial wall 516 of the ascending aorta 512. Accordingly, when a tight stenosis is encountered during angioplasty, the stenotic pushback forces can overcome the countering forces provided by the fulcrum effect of the Arani-type catheter 400.
Thus, although one can achieve and maintain deeper coaxial intubation of the tip of the Arani catheter 400 using the fulcrum technique, one sacrifices backup support because the catheter will react by moving the heel away from the postero-medial wall of the ascending aorta. Conversely, one could maintain greater contact between the heel of the catheter 400 and the postero-medial wall but would then sacrifice stable coaxial intubation. Accordingly, the Arani catheter 400 cannot simultaneously achieve the optimal combination of coaxial intubation of the tip and superior backup support desirably achieved by direct and stable contact of a heel of a catheter with the postero-medial wall 516.
This failure to achieve this optimal combination results from the inefficient configuration of the single straight tip portion 410. As the tip is further intubated into the ostium 520, the straightness and relative rigidity of tip portion 410 prevents the catheter 400 from adapting to achieve substantial and stable contact between any significant portion of the catheter 400 (usually the heel of the catheter) and the wall of the ascending aorta 512. The straightness of tip portion 410 "pulls" the heel of the catheter 400 downward to hang suspended in the ascending aorta, as opposed to the straight tip portion 410 having some curvature and the ability to flex in order to maintain backup support from the heel of the catheter during further intubation of the tip.
The straightness of straight tip portion 410 and the acute primary curve portion 408 also makes the Arani-type catheter 400 undesirable to use because they make the catheter 400 generally inconvenient to intubate the right main coronary artery 518. Because of the length and straightness of portion 410 and the 90.degree. (or 75.degree.) sharp angle of the primary curve portion 408, these portions of the catheter 400 frequently do not permit quick and easy upward or downward movement (or minimal rotation) of the tip 412 without some "lurching" of the catheter 400, i.e., the catheter catching the wall of the ascending aorta 512 during such up or down movement and then releasing forcefully because of the stored energy from "catching" the wall. This occurs because the tip portion 410 is generally designed to equal or slightly exceed the width of the ascending aorta 512 such that the tip 412 may- easily lodge into the ascending aortic wall causing the primary curve to buckle and store energy as the catheter is further advanced. This is just one of the many problems that make the Arani catheter hard to manipulate.
As seen in FIG. 2C, the buttressed position is achieved by distally advancing the Arani catheter 400 so that the secondary curve 404 of the catheter 400 contacts the antero-lateral wall 514 of the ascending aorta 512. As the catheter 400 is advanced to this position, the primary curve 408 of the catheter drops lower into the ascending aorta to be positioned within the Sinus of Valsalva 526 below the ostium 524 of the left coronary artery 522. In this buttressed position, the straight portion 406 proximal of primary curve 408 of the catheter barely contacts the postero-medial wall 516 of the ascending aorta 512 and the primary curve 408 hangs suspended within the ascending aorta 512. Any stenotic push back forces placed on the guide catheter are, in the first instance, directed downward toward the aortic valve through the straight portion instead of being directed across the ascending aorta to the postero-medial wall 516. Of course, this results in a lack of direct stable backup support for the catheter 400 in the ascending aorta 512 directly across from the right main coronary artery 518, where support is needed most.
This "dropping" of the primary curve 408 within the ascending aorta 512 also may result in the tip 412 disengaging from the ostium 520 because the straight portion 410 cannot traverse the distance from the postero-medial wall of the Sinus of Valsalva 526 to the ostium 520. Moving the catheter to a buttressed position effectively reduces the effective length of the tip 412 because at least a portion of the straight portion 410 of the tip 412 is forced at an angle upward through the ascending aorta 512 as the primary curve 408 "drops". The Arani-type catheter 400 is generally designed with a tip 412 and straight portion 410 length sufficient to extend across the ascending aorta 512 (when in- the fulcrum position) and to be capable of marginally coaxially intubating a horizontal take-off right coronary artery 518. When moved to the buttressed position, this tip 412 and straight portion 410 length are no longer adequate to extend from the postero-medial wall 516 of the ascending aorta 512 to the ostium 520 and still maintain secure and coaxial intubation of the tip 412 of the catheter 400. Consequently, if the physician chooses to maintain coaxial intubation of the tip, direct backup support will be sacrificed. Conversely, if more backup support is desired, attempts to use the buttress position will make it more likely that the tip 412 will become disengaged from the ostium 520. Accordingly, the Arani-type catheter 400 when used in the buttressed position has several problems: a lack of direct backup support, inadequate tip length, and potential angled tip entry into the ostial wall. In addition, two other significant problems with the Arani catheter as used in the buttress position results from the very sharp acute angles that are created in the body of the catheter 400 (even sharper than the already sharp 75.degree. or 90.degree. primary curve and 90.degree. secondary curve in a relaxed state). First, such acute angles greatly dissipate transmission of pushing forces for a therapeutic device extending through the catheter 400 in that position and, in the case of an acute primary curve, pushing on the catheter may cause the curve to close up or become even more acute. These factors both act to significantly limit the ability of a therapeutic device to cross a tight stenosis. Second, any rotation of the catheter 400 initiated at the proximal end gets distorted and dissipated by the sharp bends in the body of the catheter 400. These sharp angles, the contact of the secondary curve portion with the antero-lateral wall, and the absence of other curves in the catheter make it extremely difficult to further manipulate the tip 412 into and around the ostium 520 of the right main coronary artery 518 (to the extent that inadequate tip length problems can be overcome). Moreover, when in the buttressed position with the primary curve angle more acute, even if it engaged an opposite portion of the ascending aorta, the apex of the primary curve would approximate a singular point, thus not providing sufficient area for stable contact with the wall of the aorta. Accordingly, once in the buttressed position, the operator loses almost all control over the ability to position the tip of the catheter 400 and transmission of pushing forces become greatly limited. This loss of tip control can be important for reasserting intubation when the tip is too short, which is a typical problem for the Arani catheter when used in the buttressed position.
However, the problem of inadequate tip length for the catheter 400 when used in the buttressed position cannot be effectively overcome by merely lengthening straight portion 410. If this is done, then it is much more difficult to initiate intubation of the ostium 520 when initially advancing the tip 412 of the catheter 400 into the ascending aorta 512. In this instance, the straight portion 410 generally would be longer than the width of the ascending aorta, and this geometrical relationship would make it extremely difficult to initially advance the catheter 400 so that the tip straight portion 410 becomes sufficiently horizontal to enter the right coronary ostium 520.
With the catheter 400 in the preferred buttressed position (FIG. 2C), the relatively small size of the contact portion and its location substantially above (not directly across from) the ostium 520 of the right coronary artery 518 along the antero-lateral wall 514 directly contribute to the relatively poor backup support of the Arani guide catheter 400 when advancing a therapeutic device adjacent a tight stenosis. First, because the surface area of contact between the secondary curve portion 404 and the aortic wall is so small, the guide catheter 400 is unstable and therefore easier to dislodge from its position against the aortic wall when resistive "pushback" forces are encountered during advancement of a balloon catheter across a stenosis. Moreover, the straight portion 406 of the Arani-type guide catheter 400 (distal of the secondary curve 404 and proximal of the primary curve 408) extends through the ascending aorta 512, barely contacting, if at all, the postero-medial wall 516 of the ascending aorta 512. This lack of contact allows the stenotic "pushback" forces to more easily overcome the friction of the small contact area between the Arani guide catheter and the aortic wall and dislodge the Arani guide catheter from the desired orientation in the aortic complex.
Another significant problem with the Arani guide catheter, or other conventional guide catheters having 90.degree. angles and or acute angles (less than 90.degree.) along their bodies is that it may be difficult to pass some therapeutic devices (such as, e.g., stents, laser catheters, atherectomy catheters) through such sharp angles in a guide catheter. Gradual curves are required to guide these larger devices because of their increased diameter and/or attendant bulky rigid portions.